VGFacts

In the game there is a magnum-class pistol listed as Horse, this is a reference to the manga series JoJo's Bizarre Adventure, the weapon is designed similarly to the stand The Emperor, it has the name Horse wich comes from Emperor's user Hol Horse and it even has the description: "Perfect Pistol for a mercenary on a bizarre adventure." Hol Horse himself was a mercenary.

The Emperor and it's user Hol Horse:



Hol Horse summoning his Stand

Here is a video of all the weapons